Slitting device for bag-tube cut-off



July 25, 1961 Q INVENTOR:

ARD O RUPP M ATT'YS July 25, 1961 R. O- RUPP SLITTING DEVICE FOR BAG-TUBE CUT-OFF 2 Sheets-Sheet 2 Filed Aug. 4, 1958 FIG?) U mR m0 m A H m R ATT'YS 2,993,401 SLITTING DEVICE FOR BAG-TUBE CUT-OFF Richard 0. Rupp, Chicago, 111., assignor to The Cromwell Paper Company, Chicago, 111., a corporation of Illinois Filed Aug. 4, 1958, Ser. No. 752,988 Claims. (Cl. 83-l-300) This invention relates to paper-bag forming machines and particularly to devices for forming slits in the bag tube adjacent and normal to the cut-off of a bag blank.

The main objects of this invention are to provide an improved means for forming a short tab at one side of a finished bag which tab may be grasped for the purpose of pulling a tear strip along one dimension of the bag to permit the convenient separation of the bag and its contents; to provide an improved tab-forming means of this kind adapted for attachment to a conventional type of bag-forming machine which automatically severs predetermined uniform-length bag sections from continuous tubular bag stock; to provide an improved tab-forming attachment of this kind positionable on the machine to synchronize the slitting of the end of the bag, to form the pull tab, with the severance of the bag section from the bag stock; to provide an improved tab-slitting attachment of this kind which forms the tab in registration with the end of a tear tape previously applied to the inside of the tubular bag stock; and to provide an improved tab-slitting attachment of this kind which may be positioned adjustably at any desired point across the width of the bag stock.

A specific embodiment of this invention is shown in the accompanying drawings in which:

FIGURE 1 is a diagrammatic perspective of a portion of a conventional bag-stock cut-off means whereon has been positioned a tab-forming attachment constructed in accordance with this invention;

FIG. 2 is a transverse sectional view of the structure shown in FIG. 1, taken on the plane of the line 2-2 of that figure, the bag stock position just prior to severing and slitting being shown dotted;

FIG. 3 is a fragmentary, rear view taken on the plane of the line 3-3 of FIG. 2 but with the bag stock omitted;

FIG. 4 is a quarter-front view of the tab-slitting blade unit;

FIG. 5 is a plan view of the advancing end of a fiat bag tube which has been slitted to form a pull tab on the end of the next bag section;

FIG. 6 is a similar view but showing the end-opening fold made in the bag section preparatory to forming the bag end closure; and

FIG. 7 is a similar view showing the finished bag end closure.

The principal concept of this invention is to provide a conventional rotary drum type of cutter blade with a pair of axially spaced and trailing slitter knives which, in cooperation with a slotted spring plate and acting perpendicularly to the cutter blade, form a pair of parallel slits in the leading end of a continuously traveling web of tubular bag stock at substantially the instant that a preceding bag-blank length of the stock has been severed therefrom; and to arrange the slitting means so that it is adjustable, across the width of the tube stock to form the slits at substantially any desired location along the severed end.

A bag-forming machine with a tab-forming attachment A embodying the foregoing concept comprises a table 11, a pair of conventional shearing cutter knives 12 and 13, a pair of slitting blades 14, and a resilient slotted pressure plate 15.

Only a short section of the table 11, extending rearwardly from the knives 12 and 13 and the tab-forming attachment ,A, is shown- Suitable means extending for- Patented July 25, 1961 is m:

wardly of the knives 12 and 13 to receive the bag sections severed from the fiat tubular bag-stock S (shown in dotted outline in FIG. 2) would of course be provided as will be understood by those having knowledge of this art. Obviously, the table 11 would be supported on suitable framework (not here shown) extending above the table 11 adjacent the knives 12 and 13 to mount bearings (not shown) for a shaft 16 whereon a drum '17 is keyed, and to which drum the knife 13 is secured.

The knives 12 and 13 are quite similar, if not identical, in form. They are rectangular pieces of high-grade steel suitable for use in cutting the tubular bag-stock. They are tapered along one side of each to form the respective conventional cutting edges 18 and 19.

The knife 12 is secured to a suitable mounting block 21, below the table 11, with its rear edge abutting a ridge 22 on the block 21, and the knife 12 is so disposed at an upwardly-inclined angle that the cutting edge 18 is substantially in the plane of the top of the table 11 vertically below the axis of the shaft '16 (see FIG. 2).

The knife 13 is secured to a longitudinal rib or extension 23 on the drum 17 in radial relation with the drum 17 and its supporting shaft 16. Also, the radial positioning of the knife 13 is such that the cutting edge faces forwardly of the direction of travel of the bag-stock on the table 11, so as to present the cutting edge 19 in a vertical plane embracing the cutting edge 18 of the knife 12 and the axis of the drum shaft 16 (FIG 2).

The slitting blades 14 are secured to parallel opposite lateral faces of a mounting block 24 shaped on its forward face to fit a longitudinal recess 25 in the drum and against the back side of the rib 23. Each of the blades 14 lies in a plane normal to the axis of the drum 17 and is somewhat L-shaped to fit around the lower portion of the drum rib 23 and dispose the radially outward perim eters 26 of these blades 14 rearwardly from the advancing end 27 which abuts the rear face of the knife 13. The lower forward portion of each blade 14 is preferably tapered to form a cutting edge 28 extending angularly rearward from the advancing end 27.

As shown, the mounting block 24 is formed with an aperture for the insertion of a machine screw 29 receptive in any of a series of threaded holes 31, extending longitudinally along the rear face of the rib 23 (FIG. 1). This permits the location of the slitting blades at any of variously selected points longitudinally of the cut-off blade 13 and transversely of the bag stock S (FIGS. 5, 6 and 7).

The slotted spring plate 15 is a strip of resilient material, preferably metal, here shown slotted to form three resilient tongues 32 extending forwardly from a base section 33. The tongues 32 are permanently biased to the base section 33 to extend upwardly forward of the table 11 when the base section 33 is secured to the table 11.

The front-to-rear dimension of the flanged plate 15, and its positioning on the table 11, disposes the free ends of the tongues 32 closely adjacent the rear face of the knife 13 when in its vertical bag-stock cutting position and the bag stock has. depressed the tongues (FIG. 2), as will be explained presently, and the depth and spacing of the slots is such as to freely pass the slitting blades 14 as the drum 17 rotates. I

As shown, the base section 33 of the plate 15 is formed with apertures for the insertion of a pair of machine screws 34 receptive in any of a series of threaded holes 36 (FIG. 1), extending transversely across the table 11, adjacently rearward of the knives 12 and 13, in correspondingly spaced relation with the slitter blade mounting holes 31 in the rib 23. Thus the plate 15 is positionable on the table 11 to align the slots between the fingers 32 with the blades 14 at any of variously selected points along the length of the cut-off knife 13 that the slitter blade mounting block 24 may be located.

Bag-stock S, on which this tab-slitting attachment A is adapted to form tabs 30, is conventional flat tubular stock caused to continuously move along the table 11 by a conventional feed mechanism (not shown). Such tubular stock is made by folding over lateral portions of a sheet of material (see FIGS. 5, 6, and 7) and suitably adhering their overlapping margins. Incident to thus forming the flat tubular bag-stock, and prior to folding the lateral portions of the initial sheet, a tear strip 37 of a relatively strong material is adhered, in a conventional manner, longitudinally along the inner face of the sheet stock so as to be at a desired position transversely of the formed tube on the interior thereof.

As the several sections of this bag-stock are cut off by the main blade 13, they are made into bagsby closing the leading or advancing ends in any of several ways known and practiced in the bag-forming industry. FIGS. 6 and 7 show two successive steps whereby the leading ends of the bag section are folded, overlapped and adhered together to form what is known as a satchel-bottom, the formed tabs 3% appearing at the advancing ends of the bag stock in register with the tear strip, as shown in FIG. 5, and being at all times accessible at the edge of the outermost folded flap of the finished bag bottom as shown in FIG. 7.

The operation of a bag-forming machine with a tabforming attachment A constructed in accordance with this invention, is substantially as follows:

As indicated in dotted outline in FIG. 2, the fiat, tubular bag-stock 8 moves longitudinally along the table 11 under constant, uniform speed.

As the drum l7 revolves, in the direction of the arrow 38, the knife 13, approaches the bag-stock S extending up over the ends of the tongues 32 and across the stationary blade 12. Upon contact of the knife 13 with the bagstock, and the continued forward movement of the knife, the bag-stock and the tongues 32 are gradually depressed downwardly to near contact with the table 11. Trailing the knife 13, the slitting blades 14 continue to press the stock S and the tongues 32 down firmly against the table, the blades 14 engaging the portions of the stock between the tongues 32.

At the instant the cutting edges 18 and 19 of the respective knives l2 and 13 move into a vertically-aligned position the bag-stock is severed and an appropriate baglength of the stock is cut off. The advancing transverse edge of the remaining stock is concurrently released and the upward force of the compressed resilient tongues 32 drives this advancing edge of the stock upwardly against and past the cutting edges 28 of the blades 14 causing a pair of spaced slits 39 to be formed inwardly from the edge of the advancing stock to produce the tab 30. This slitting action occurs at substantially the instant that the preceding bag-length of the stock is severed and hence automatically prepares the leading edge of the next baglength to be formed so as to provide the free pull tab 30 at the bottom of the bag, perfectly aligned with the tear strip 37, as shown in FIG. 7. The knife 13 and the blades 14 continue their rotative movement up and away from the bag-stock preparatory to a repetitive action as above described. The rotation of the knife blade drum 17 is, of course, correlated with the speed of travel of the bag-stock web S to provide cut-off sections of the stock of proper length to form the desired bags, as will be understood by those acquainted with this art.

The motion of the cutting knife 13 is such that its path from its severance position (aligned with knife 12, as shown in FIGS. 1 and 2) to its tongue-depressing position is different from the path it takes from the tonguedepressing position to its severance position. Such a motion may be termed a closed path.

It will now be seen that the slitting operation performed by the herein described mechanism is direct shearing action resulting from the snapping upwardly of the tongues 32, which drives the paper Web or stock over the cutting edges 28 of the blades 14, forcing the blades through the advancing margin of the stock while the blades are simultaneously moving in a forward direction. The paper stock is, of course, also moving in the same direction and at substantially the same speed. Thus the length of the slits is determined entirely by the length of the cutting edge on the slitting blades.

The main advantages of this invention reside in the extremely simple form of the apparatus involved; in the fact that the slitters are directly mounted on the main cut-off knife and perform their function simultaneously with that of the cut-off knife; in the fact that the slitting means is readily adjustable to accommodate substantially any location of the tear strip transversely of the web of tubular bag stock; and in the fact that the need for a separate or independent tab forming station on the bag making machine is completely obviated.

Although but one specific embodiment of this invention is herein shown and described it will be understood that details of the structure shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.

I claim:

1. A bag tab-forming machine comprising, a supporting table along which bag stock is movable, a first knife fixed on a mounting arranged transversely of the table and movable in a closed path into and out of position substantially at the plane of the table for severing bag length sections from bag stock supported by the table, a pair of laterally spaced blades attached to the first knife mounting in a position normal to the knife and projecting rearwardly therefrom, a resilient plate fixed to the table rearwardly adjacent the bag stock severance position of the first knife for traverse of the bag stock over the plate as the bag stock is moved along the table, the plate having an upwardly and forwardly inclined portion disposed in the path of said blades and forwardly opening slots therein registering with the respective blades to provide upwardly inclined tongues to extend between and at the sides of the blades, which tongues normally hold the bag stock spaced above the table adjacent the severance position, the tongues being of a length to be depressed by the first knife in its contact with the overlying bag stock as the knife approaches the severance position whereupon the resulting severance of the bag stock releases the tongues to snap the severed end of the bag stock against the blades and cause them to cut short longitudinally extending slits in the leading end of the bag stock.

2. The machine of claim 1 wherein said knife is movable in a rotatable path.

3. The machine of claim 2 including a second knife fixed transversely of the said supporting table, said knives coacting for severing bag stock on the table into bag length sections.

4. The machine of claim 3 including means for adjust ably positioning the blades and plate in selected aligned positions transversely of the table to vary the location of the tab being cut in the end of the bag stock.

5. The machine of claim 4 wherein the pair of laterally spaced blades is secured to a mounting block, a threaded fastener securing the mounting block to the said mounting, the resilient plate secured by a threaded fastener to the table and wherein the said means comprises a series of uniformly spaced threaded holes on the knife mounting therealong and rearwardly of the said first knife, the table having a series of equally uniformly spaced threaded holes extending transversely of the table rearwardly of the severance position, the mounting block and the plate being adapted for aligned positioning at selected positions transversely of the table to vary the location in the leading end of the bag stock at which the tabs will be cut.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS 6 Bauer Mar. 3, 1931 Topping Oct. 2, 1934 Ellis Oct. 15, 1940 Sandberg Mar. 20, 1945 Smith July 13, 1954 

